The present invention relates to fetal stimulation and testing devices, and more specifically to an ultrasound device for stimulating a fetus in utero and for monitoring movement of the fetus as a result of the stimulation.
Audio fetal stimulators are commonly used in clinics to evaluate both the general health and hearing of fetuses in utero. Audio stimulation devices can include both artificial larynxes and devices which employ speakers to xe2x80x9ccommunicatexe2x80x9d with the fetus, such as those described in U.S. Pat. Nos. 6,169,814 and 5,913,834. In each of these devices, an audio sound source is generated externally and is transmitted into the abdominal cavity of the mother to stimulate the fetus. Movement of the fetus can be monitored to track reaction to the audio stimulation, and therefore to verify general hearing, assess fetal health based on response to the stimulation, and to analyze other parameters.
While these audio stimulation devices are useful for general testing of both the overall hearing and response of the fetus, there are certain limitations associated with audio stimulation devices of the type described above. These devices, for example, produce sound which is transmitted to the abdominal cavity with little or no directivity. Because the audible sound has very long wavelengths, it tends to spread equally in all directions in the abdomen. Therefore, when audio stimulation is applied to test hearing, the sound is transmitted simultaneously to both fetal ears. It is not possible to test each of the ears individually. Furthermore, although the sound stimulation causes the fetus to move, prior art methods are not designed to cause the fetus to move to a particular position or location in the uterus. Because the sound is almost non-directional, there is no xe2x80x9cquietxe2x80x9d place in the uterus at which the fetus would feel less stressed. Hence the fetus moves almost randomly to the audio stimulation.
The present invention is a method and apparatus for audio stimulation of a fetus in utero. The fetal stimulator of the present invention produces fetal auditory stimulation by direct conversion of ultrasound energy to audible sound waves. Hence the fetal stimulator of the present invention can be used to stimulate the fetus in a very specific region.
In the present invention, a focused ultrasound transducer is driven by an amplitude-modulated signal to provide localized, directed energy to the fetus. An RF generator provides a carrier signal at the ultrasound frequency, between 1 and 10 MHz, and an audio a modulation generator provides a modulation signal. An amplitude modulator modulates the carrier signal with the audio signal to produce a modulated signal. The resultant modulated signal is used to drive the ultrasound transducer. The transducer, which is positioned on the abdomen of the mother, produces a single focused beam which can be aimed at the fetal head, the ear, or other selected location.
Movement of the fetus can be monitored in a number of known ways, movement can be monitored, by the mother, which provides an indication when she senses fetal movement. Alternatively, fetal movement can be monitored by a Doppler fetal monitor, through analysis of Doppler shift data from applied and received signals, and by synchronization to a heart beat of the fetus. The fetal stimulator described above can be applied in a number of different clinical applications, and is particularly suited for use in assessment of the hearing and general health of a fetus.
It is an object of the invention to provide a method and apparatus for selectively applying a highly localized, highly directive, and calibrated energy beam to a fetus.
It is another object of the invention to provide a method and apparatus for monitoring motion of a fetus in conjunction with the application of a highly localized, highly directive ultrasound beam.
It is yet another object of the invention to provide a method and apparatus for individually testing the hearing in each of the ears of a fetus in utero.
It is still another object of the invention to provide a method and apparatus for repositioning a fetus in the womb.
It is yet again another object of the invention to provide a method and apparatus for testing the general health of a fetus.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims herein for interpreting the scope of the invention.